Spectroscopic ellipsometry characterization of PbWO4 single crystals

Delice S., Isik M., HASANLI N., Darvishov N., Bagiev V.

Optical Materials, cilt.131, 2022 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 131
  • Basım Tarihi: 2022
  • Doi Numarası: 10.1016/j.optmat.2022.112680
  • Dergi Adı: Optical Materials
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, PASCAL, Aerospace Database, Applied Science & Technology Source, Communication Abstracts, Computer & Applied Sciences, INSPEC
  • Anahtar Kelimeler: Optical properties, Tungstate, Ellipsometry, PbWO4, LUMINESCENT PROPERTIES, OPTICAL-PROPERTIES, REFRACTIVE-INDEX, THIN-FILMS, LEAD, SCHEELITE, NANOSTRUCTURES, SCINTILLATORS, ABSORPTION, PARAMETERS
  • Orta Doğu Teknik Üniversitesi Adresli: Evet

Özet

© 2022 Elsevier B.V.Optical characterization of PbWO4 single crystals grown by Czochralski method was achieved in virtue of spectroscopic ellipsometry experiments carried out in the energy region of 1.0–5.6 eV at room temperature. Tetragonal scheelite structure with lattice parameters of a = b = 5.4619 Å and c = 12.0490 Å was determined for the bulk crystal utilizing from XRD analysis. Analyses of the ellipsometry data presented the photon energy dependencies of complex dielectric function of the crystal. The real part of the dielectric function exhibited increasing behavior with energy in the below 4.1 eV and then decreased immediately. Zero frequency refractive index and dielectric constant were determined to be 2.02 and 4.08, respectively, using Wemple and DiDomenico oscillator model. High frequency dielectric constant was calculated as 4.30 by Spitzer-Fan model. Optical band gap of PbWO4 was found to be 3.24 eV from the dielectric relaxation time spectrum. Moreover, existence of two critical points with energies of 3.70 and 4.58 eV was revealed from the analyses of extinction coefficient and second derivative of the dielectric function. These levels were considered to be due to creation of cation exciton (Pb2+ 6s2 − Pb2+ 6s6p) and transitions in the [WO4]2− group.